Front packers are provided for ram-type blowout preventers on drilling equipment for sealing an annulus about a tubular member such as a drill pipe. A ram-type blowout preventer has two opposed ram blocks mounted for inward movement toward each other for sealing engagement with the pipe. Each ram block includes a packer formed of an elastomeric or hard rubber material for engaging the outer periphery of the pipe to form a tight seal. Each packer has a semicircular opening or recess to receive the pipe and form a tight seal about 180.degree. of the outer periphery of the pipe.
During a stripping operation, the drill pipe is pulled from the well bore with the blowout preventer engaged against the drill pipe. Frictional contact between the blowout preventer and the pipe during stripping may result in considerable wear against the packer. For that reason, a wear insert may be added to the packer for contacting the pipe. For example, as shown in U.S. Pat. No. 4,398,729 dated Aug. 16, 1983, an insert is provided formed of a suitable resilient material which may include a nylon and/or urethane material. The combination of the packer and its insert may be called a "packer assembly". Such an insert is received within a recess in the packer. It is forcibly urged against the elastomeric packer when contacting the drill pipe under substantial fluid pressure from the ram operating piston. The insert illustrated in U.S. Pat. No. 4,398,729 includes a pair of integral outwardly extending projections. The packer is formed with a pair of coacting receptacles or grooves to receive the projections of the insert. The resilient insert is depressed inwardly when its projections are initially inserted within the receptacles in order to provide yieldable cooperation between the insert and the packer. The interfitting projections and receptacles secure the insert within the recess of the packer and prevent relative movement of the insert and the packer during rotation of the drill pipe while in frictional contact with the insert.
U.S. Pat. No. 5,127,623 dated Jul. 7, 1992 shows an insert for a front packer assembly in which an elastomeric packer member is formed with slots to receive projecting lugs of an insert to position the insert accurately within the packer member and prevent relative rotation of the insert and packer member. The insert is held in place by screws.
U.S. Pat. No. 4,541,639 dated Sep. 17, 1985 likewise shows a replaceable insert for packer assembly with projecting portions that fit into mating recesses or receptacles formed in the elastomeric packer member for retaining the insert therein.
Thus, prior means for retaining a replaceable wear insert within a recess of a front packer member have either (1) used separate retainers, such as nails or screws, extending through the insert and anchored in the adjacent elastomeric packer member or (2) employed separate preformed receptacles or recesses in the elastomeric packer member to receive projections on the insert in an interfitting relation.